Ahem et al. (2010) conducted a cross-sectional analysis to determine if there was significant presence of low birth weight in mothers living near coal mining areas in West Virginia. After adjusting the findings so that mothers who reported smoking or drinking were accounted for, they found that areas with high levels of coal mining elevated the odds of a low-birth-weight infant by 16- 14% (with the lower percentage adjusted for mothers who drank) in areas with lower mining levels, relative to counties with no coal mining.
Ahem, M. Hamilton, C. Mackay, K. Mullett, M. 2010. Residence in coal-mining areas and low-birth-weight outcomes. DOI 10.1007/s10995-009-0555-1
Coal mining releases toxic chemicals including arsenic, mercury, lead, cadmium, selenium, nickel, and copper into local environments, and the processing of coal involves the use of other toxic chemicals like acryamilides, complex polymers used to separate the coal from the sludge. These compounds are called “trade secrets” by many coal companies and given nicknames like “Comax 1000”. This is in addition to the diesel fueled equipment that moves and processes coal. Materials rejected by a cleaning plant tend to be enriched in iron sulfides which oxidize into sulfates, causing the acidification of water that comes into contact with refuse piles. Contaminated water is held in impoundment ponds, or injected underground so as to not accidently become a potable water source.
In West Virginia, mountaintop removal mining has become an increasingly dominant form of coal mining. This form relies on surface explosives and removal of up to 1,000 feet of rock and soil above the coal. While this is an easier and less cost intensive method of reaching coal beds compared to underground mining methods which tunnel into mountains via the sides, levels of airborne particulates are higher in surface mining vs. underground mining operations and result in community level exposure. This is an important point because recent studies have documented significant transplacental transfer of contaminants, including polycyclic aromatic hydrocarbons (PAHs) and environmental tobacco. In addition, the fetus may be vulnerable to pollution stored inside the mother’s body; further research on it will be covered later in this chapter.
Birth data were obtained from the West Virginia Birthscore Dataset, 2005–2007 (n = 42,770) while data on coal mining were taken from the Department of Energy, Energy Information Administration (EIA). Covariates regarding mothers’ demographics, behaviors, and insurance coverage were included. Mothers who were older, unmarried, less educated, smoked, did not receive prenatal care, were on Medicaid, and had recorded medical risks had a greater risk of low birth weight were not included in the study, reducing the data set from about 45,000 to 42,770.
Birth weight was converted to a yes/no score based on whether birth weight was less than 2,500 g. The independent variables were counties with zero, moderate, or high levels of coal mining. Counties with coal mining were divided into levels of coal tonnage, and the mother’s age was converted into younger than 18, 18–39, and 40 and older. Number of previous pregnancies was recorded, including live births, abortions and stillbirths for mothers residing in mining areas.
The results showed a significant association between receiving late prenatal care and elevated risks for low birth weight outcomes. Mothers in mining areas were also found to be at a significantly higher risk of low birth weight before controlling for covariates. Further, there is evidence of a dose response effect, meaning that there was a higher odds ratio of low birth weight in areas of higher levels of mining compared to areas of moderate mining levels. The risk of low birth weight was found to be related to previously established factors as expected.
Before adjustment, living in a high coal mining area increased the odds of a low birth- weight infant by 19%; after adjustment, the odds were still elevated by 16%. For areas with lower mining levels, the odds of a low-birth-weight infant were increased by 13% before adjustment and 14% after adjustment.
Future research needs to refine categories of medical risks to understand the contribution of each of these risks on low birth weight outcomes. In addition, the level of coal mining served as an environmental proxy for air and water contamination, because no direct environmental data related to levels of air particulates or types of water contamination were available. Recent studies have examined the impact of polycyclic aromatic hydrocarbons (PAH’s) and fine particles on pregnancy outcomes, finding support for the idea that adverse pregnancy outcome is the result of maternal exposures to airborne particulates themselves, vs. the impact of co-pollutants carried by the particles.